1. Field of the Invention This invention relates to variable color optical devices.
2. Description of the Prior Art
A display device described in U.S. Pat. No. 3,740,570, issued on June 19, 1973 to George R. Kaelin et al., uses special LEDs that exhibit different colors when subjected to different currents. The LEDs are biased by pulses of different amplitudes to achieve different colors of the display.
A circuit employing a dual-color LED driven by a dual timer is described in the article by Bill Wagner entitled 2-color LED+driver=versatile visual effects, published on Oct. 2, 1980 in EDN volume 25, No. 19, page 164. Since dual-color LEDs are connected to conduct currents in opposite directions, it would be impossible to forwardly bias them simultaneously.